The temporal lobe is the second largest lobe of the cerebrum. It performs several important functions.
What is the temporal lobe?
The temporal lobe is also known as the temporal lobe, temporal brain, or temporal lobe. It forms part of the cerebrum and is its second largest lobe after the frontal lobe. The temporal lobe is considered a varied component of the human brain, both in its functions and anatomically. Thus, it contains important memory structures, the Wernicke language center, and the primary audiotor cortex. The temporal lobe forms the lower and lateral section of the cerebrum. Its demarcation is against the frontal lobe (lobus frontalis) and the parietal lobe (lobus parietalis). On the posterior side, it is demarcated by the occipital lobe (lobus occipitalis).
Anatomy and structure
The temporal lobe is found within the middle cranial group, also called the fossa cranii media. Most of the temporal lobe is located in the area above and just in front of the ears. Towards the vertex and occiput, it merges into the parietal lobe and occipital lobe. The fissura lateralis, a deep furrow, provides separation between the temporal lobe and the frontal lobe. In its depth is the insula. The two temporal lobes frame the brainstem. On the lateral surface of the temporal lobe, there are usually three brain convolutions as well as two furrows. These are the superior temporal gyrus, the medial temporal gyrus, the inferior temporal gyrus, and the superior and inferior temporal sulcus. A similar surface relief is found on the medial surface of the temporal lobe. These are the parahippocampal gyrus including the uncus, the occipitotemporal gyrus medialis, also called the forsiform gyrus, and the collateral and lateral occipitotemporal sulcus. Both the posterior medial part and the basal part of the temporal lobe receive their blood supply from the posterior cerebral artery (ACP). The branches of the middle cerebral artery are responsible for the blood supply of the anterior middle section and the lateral part. Venous blood is collected by the media superficial vein and the descending cerebri superficial vein in the cavernous sinus and in the transverse sinus.
Function and Tasks
The temporal lobe performs several important functions. First and foremost among these is hearing. Thus, the primary auditory center is located within the deep lateral fissure. In the convolutions, it comes to the terminal portion of the auditory pathway. This is responsible for transmitting signals from the sensory cells in the cochlea. The primary auditory center is also called Heschl’s transverse convolutions and reaches only the size of a postage stamp. The tertiary and secondary audiotor centers, located in the middle and upper convolutions of the temporal lobe, are much larger. Almost the entire cortical area of the temporal lobe is occupied by them. At the transition point between the middle and superior temporal convolutions to the cortices of the posterior lobe, the overlap of audiotor and visual functions occurs. This is also where lexical centers are located. They serve to recognize spoken and written words. The best known center is the Wernicke sensory speech center. It is mostly located in the left hemisphere. Another important task of the temporal lobe is smelling. The olfactory pathway finds its end at the uncus (hook). The uncus is a small protrusion that faces inward. Below the olfactory cortices is the amygdala, which is functionally part of the limbic system. Among other things, the amygdala is responsible for the sensation of fear. The temporal lobe is also extremely important for human memory. This is especially true for the parahippocampal gyrus, where the entorhinal cortex is located. This forms an interface, so to speak, between things that have just been experienced and memory. Thus, the entorhinal cortex and the hippocampal formation provide for the input of new memory content and the retrieval of pre-existing memories. Despite the wealth of knowledge about the temporal lobe, it is still not known exactly what functions are performed in its anterior areas.
Diseases
Because the temporal lobe performs numerous important functions, traumatic lesions can lead to consequential disorders of this brain structure. The first known case of disease was in Henry Gustav Molaison (1926-2008), an American laborer. Molaison suffered from epilepsy that could not be successfully treated. For this reason, he underwent surgical removal of the medial portions of both temporal lobes in the 1950s. Following the procedure, Molaison experienced significant anterograde amnesia. Thus, the patient was unable to incorporate newly learned items into his long-term memory. Among the most common temporal lobe impairments is temporal lobe epilepsy. In this case, the epileptic seizures originate in the amygdala, the hippocampus and the adjacent convolutions. With a share of 27 percent, temporal lobe epilepsy is the most common localization-related epilepsy. Typical features of epileptic seizures include the occurrence of visceral auras and unpleasant sensations in the stomach area. This is followed by smacking-chewing mouth movements, movements all over the body, and loss of consciousness. Drug treatment of temporal lobe epilepsy is considered difficult. If a lesion occurs in the associative temporal cortex, it often results in audiotor and visual disturbances. This becomes noticeable through problems in identifying faces or objects. Sometimes, melodies, rhythms, or sounds can no longer be recognized.
